Method of making screws and bolts



1,617,122 J c. KAUFMAN METHOD OF MAKING SCREWS AND BOLTS Filed Sept. 8,1925 Inven' l Km M MW Patented F eb. 8,1927;-

UNITED STATES CHARLES KAUFMAN, or CLEVELAND, 01110.

METHOD OF MAKING SCREWS AND BOLTS.

7 Application filed September a, 1925. Serial m. 54,953.

This invention relates to a method of making certain kinds of screws andbolts having. an unthreaded portion next to the threads, such as capscrews, machine bolts,

form the blanks that they are held to exact dimensions, and so thatthycan' be formed in any lengths desired, and at the same-time permit abetter and larger head to be formed which does not crystallize orfracture in forming. Y

These screws and bolts are commonlyformed from a length of wire of adiameter corresponding to the pitch diameter of the thread to be formed,and by means ofdies a portion of the blank is upset to form the head andalso to form an enlarged portion between the head and the portion tobethreaded, said enlarged portion being expanded by the upsetting processto the external diameter of the threads which are to be rolled onto thatportion of the blank which remains at the original diameter.

Instead of starting with ablank which is of the pitch diameter of thethread to be formed, and then upsetting the stock to enlarge the same toform the unthreaded portion and the head, I start with a length of stockwhich in diameter corresponds to the diameter of the unthreaded portionof the finished .screw or bolt, and reduce that portion of the blankwhich is to be threaded, the part to bethreaded being reduced to thepitch diameter of the thread to be formed. Preferably the reducing ofthe part to be threaded is accomplished in the same dies and at the sametime that the other end of the stockis upset to form the head. a

The invention may be further brieflysummarized as consisting in thesteps of the improved method which will be described in thespecification and set forth in the appended claims.

In the accompanying sheet of drawings, Fig. 1 shows a length of wireready for the forming process; Fig. 2 shows the blank after the stock ofFig. 1 has been treated by my improved method; Fig. 3- shows thefinished screw, in this instance a cap screw; and Fig. 4 showsdiagrammatically a pair of dies which may be utilized in carrying out myimproved method.

The screw which is produced is of con- 'ventional shape or design, andconsists of a head 10,-a threaded portion 11 and an unthreaded portion12 between the head and threaded portion. If the threads are formed by arolling process, as is customary, the portion 12 must beof greaterdiameter than the portion to be threaded, and as before stated, the head10 and portion 12 are generally formed by expanding the stock, the

original diameter corresponding to the pitch diameter of thethreadedportion.

Inasmuch as the head 10 and unthreaded portion 12 are by the commonlyemployed method both formed by expanding or enlarging the stock,practice has demonstrated that the length of the unthreaded portion islimited, i. e. can not be made in more than a predetermined length for agiven size of stock, and inasmuch as the head is formed from a stock ofrelatively small size, it is generally not perfectly formed and oftencrystallizes or fractures in the forming.

According to my invention I start with stock or length of wire indicatedat 13 in Fig. 1, and produce the blank shown in Fig. 2, by a methodwherein'the diameter of the portion 15 to be threaded is reduced, whilethe enlargement 16.to form the head of the finished screw is formed byupsetting the stock of the original diameter. That is to say, if Drepresents the diameter of the stock 18, this diameter is maintained inthe portion 14, while the portion 15 to be threaded,.is reduced to asmaller diameter d, and the head portion 16 is upset to a, largerdiameter D.

In carrying out the method I prefer to use :male and female dies,indicated convention- In practice the wire is fed in an indeterminatelen h from a suitable reel, and is automatica ly cut into sections ofthe desired length, and asa section of stock is cut off it is carriedover into line with the cavity of die 17, which is the stationary die.The

die 18 reciprocates, and as soon as the stock comes into line with thecavity it is struck by the die and driven inward, a portion of the stockbeing forced into the reduced part 17 of the cavity so as to formtheportion i of the blank by reducing the diameter of I At the same timethat the stock is form orpartially form the head 16. The

blank is head may be entirely formed by this same blow of the die orplunger 18, but generally the stock is given a second blow to completethe formation of the head, after which the blank is ejected. I

"By this method the reduced part 15 of the iven a skin or surfacehardening character stic of drawn or extruded material, which makes itvery desirable for screw forming purposes, and inasmuch as, the portion14 retains its original diameter, it is, of course, possible to makethis of any length, as is true also of the reduced part 15. On thecontrary, by the old method wherein the diameter of the portion 14 isformed by the upsetting process, the length of the unthreaded portion ofthe blank is limited. Furthermore, since the diameter of the portion 16'is unchanged, and the portion 15 formed by driving the stock into thereduced part of the die cavity, it is obvious that the blanks can beturned out, one after another, with the portions 14 and 15 held to theexact dimensions desired, which is not always the case with the priorprocess, and since the head 16 is formed from stock of a larger diameterthan is used with the old process in forming a given sized screw,thereis less likelihood of crystallization and fracture in formingthehead.

In brief,'therefore, by my method above described, I am able to producebetter and more accurate screws or bolts than heretofore, with a.minimum loss on account of defective blanks, and with any desired lengthof unthreaded portion, and at the same time'the blanks can be producedwith the same or greater rapidity than by the prior .methods. Afterthe'blank described above, and illustrated in Fig. 2, is formed, thescrew is fi'nished by converting, by the usual process,

the annular head 16 to an octagonal or other the reduced portion and.the enlarged head polygonal shape des ed if th type of screw requiresit, and by forming the thread 11 on the reduced part-.15 of-the blank,generally by rolling the thread thereon.

As already stated, the stock from which the screws areforlnedcorresponds in size to the diameter of the unthreaded portion, but thestock may have a slight oversize or undersize tolerance. If it isslightly oversized, the stock will be forced into the die-cavity by theplunger 18 slightly reducing thestock to the amount of the tolerance toform the portion 14: of theblank. If the stock is slightly undersized,the stock is slightly enlarged to completely fill the portion 17 of thedie cavity. Generally the original diameter D of the stock is maintainedin the portion 14 of, the blank, but as stated above,

a slight variation in the size of the stock, either oversize orundersizewill have no material effect on the method since the most importantfeature of the invention is the reduction and lengthening and consequenthardening of that part of the stock which is to be threaded. x

While I have illustratedmy method applied to the production of capscrews, it can be used just as effectively for forming other types ofscrews and bolts such as those mentioned in the early part of thespecification. While I have described the preferred method of carryingout my invention,I do

not desire to be confined to the precise details shown, but aim in myclaims tocover all modifications which do not involve a departure fromthe spirit and scope of my invention. a

Having described my invention, I claim: 1. The method of making screwsand bolts, which comprises upsetting one end of a length .of stock toform the" head-portion and in the same operation drawing out and therebylengthening and reducing another portion to the pitch diameter of thethread to be formed by forcing the stock endwise into the opening of adrawing die, and forming the thread on said portion.

' 2. The method of making screws and bolts, which comprises forcing apiece of stock w by pressure exerted endwise thereon into the opening ofa drawing die to drawout and thereby reduce and lengthen the portionwhich is to be threaded, and in the same operation upsetting upon oneend an enlarged head portion, and thereafter 2 forming the thread onsaid-reduced portion.

3. The method of making screws and bolts which comprises forcing a pieceof stock by pressure exerted-endwise thereon into the opening of adrawing die to draw out and 5 thereby reduce. and lengthen the portion.which is to be threaded, and in the same operation upsetting upon oneend an enlarged head portion and retaining a portion between portion ofsubstantially the same-diameter as the diameter of the iece of stock,and thereafter forming the t read upon the re; duced portion.

4. The method of making screws and bolts, which comprises forcing apiece of stock by pressure exerted endwise thereon into the opening of adrawing die to draw out and thereby reduce a portion to a diametersubstantially equal to the pitch diameter of the thread to be formed,and in the same operation upsetting an enlarged head portion upon oneend, and retaining a portion between the reduced portion and theenlarged head portion of a diameter substantially equal to the diameterof the piece of stock, and thereafter forming the thread upon saidreduced portion.

5. The method of making screws and bolts,

whieh comprises forcing a piece of round wire or rod by pressure exertedendwise thereon into the opening of a drawing die to draw out andthereby reduce the portion to be threaded and in the same operationupsetting an enlarged head portion upon one end but retaining anintermediate portion of a diameter substantially equal to the diameterof the wire or rod, and thereafter rolling a thread upon said reducedportion.

In testimony whereof, I hereunto atfix my signature.

CHARLES KAUFMAN.

